quantization: Linear + BatchNorm1d fusion (#50748)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50748
Adds support for Linear + BatchNorm1d fusion to quantization.
This is a redo of dreiss's https://github.com/pytorch/pytorch/pull/37467, faster
to copy-paste it than rebase and deal with conflicts.
Test Plan:
```
python test/test_quantization.py TestFusion.test_fusion_linear_bn_eval
```
Imported from OSS
Reviewed By: supriyar
Differential Revision: D25957432
fbshipit-source-id: 24e5b760f70186aa953ef65ab0182770e89495e4
